This invention relates generally to improvements in catheters of the type used to administer a selected medication to a patient over an extended period of time. More specifically, this invention relates to a medication infusion catheter having an improved distal end tip which permits, on an as-needed basis, expulsion of an occlusive deposit.
Catheters are well-known in the medical arts for use in delivering medical fluids to or drawing body fluids from a patient. In one typical form, the catheter comprises an elongated tubular element adapted for transcutaneous placement, normally with the assistance of a withdrawable stylet needle. The catheter defines a narrow lumen or passage permitting transcutaneous fluid transfer to or from the patient. In another typical application, the catheter is implanted into the patient in association with an implantable infusion pump or similar instrument for programmed delivery of a selected medication such as insulin over an extended period of time. One such implantable infusion pump including an implantable catheter is shown, by way of example, in U.S. Pat. Nos. 4,373,527 and 4,573,994. In either case, the catheter is commonly constructed from a biocompatible polymer material, such as a medical grade silicone rubber.
In many patient treatment applications, it is necessary or desirable for the catheter to remain in place over an extended period of time which may range from several days to several years. One such long term application includes use in combination with an implantable medication infusion pump, as described above. In long term indwelling applications, however, the distal end tip of the catheter is susceptible to occlusions which appear to occur as a result of complex interactions involving the catheter material, and/or the simultaneous presence of infusion and body fluids. The likelihood of occlusion development appears to be increased when complex medications such as insulin are delivered to the patient. When an occlusion occurs, normal medication delivery to the patient is obstructed or prevented. Catheters have not been designed to provide an effective or practical way to achieve in situ occlusion removal. Surgical removal and replacement of a clogged catheter is not a desirable alternative.
There exists, therefore, a significant need for improvements in long term indwelling catheters, particularly with respect to providing a catheter tip which will facilitate and permit expulsion of an occlusive deposit. The present invention fulfills this need and provides further related advantages.